21. It is the first time that I ______ this kind of moon cake.
A. enjoyed B. have enjoyed C. had enjoyed D. enjoy
22. There was ______ time ______ I hated to go to school.
A. a; that B. 不填; when C. a; when D. the; when
23. ______ the students who took part in the training is 450.
A. A number of B. A lot of C. Lots of D. The number of
